Flow Chart of the Mill

Although the Mill was huge and filled with hundreds of large, noisy machines, the job the Mill performed was rather simple. The top six levels were used to crush and grind large pieces of mined rock into a powder. The froth flotation process took place on the seventh level. In this process, ground up rock was mixed with water and special chemicals. Air bubbles were pumped through the mixture, and the chalcopyrite ore, which contains the precious copper minerals, stuck to the bubbles and rose to the surface where it was skimmed off. On the bottom level of the Mill, the concentrate, as the ore was now called, was dewatered in large thickening tanks. These thickening tanks turned slowly, causing the heavy ore to sink to the bottom and water to rise to the top.

The concentrate was then sent to smelters all around the world. There the minerals were heated to high temperatures, purified into copper and sold.

Modern mills use a very similar process, although today, chemicals and machines are more efficient. Minerals are crushed, separated, dried, then heated to high temperatures, or smelted, to purify them into finished consumable metals such as copper. The simplicity of this process allowed the Mill at Britannia to operate with many of the same machines for 50 years. Click here to view a printable PDF version of the Mill Flow Chart.